An ever increasing emphasis is being placed on systematic monitoring of environmental conditions in relation to ground and surface water resources. Examples of some situations where monitoring of conditions of a water resource may be desired include environmental monitoring of aquifers at an industrial site to detect possible contamination of the aquifer, monitoring the flow of storm water runoff and storm runoff drainage patterns to determine the affects on surface water resources, monitoring the flow or other conditions of water in a watershed from which a municipal water supply is obtained, monitoring lake, stream or reservoir levels, and monitoring ocean tidal movements.
These applications often involve taking data over an extended time and often over large geographic areas. For many applications, data is collected inside of wells or other holes in the ground. A common technique is to drill, or otherwise excavate, a number of monitoring wells and insert down-hole monitoring tools into the wells to monitor some condition of the water in the wells. One desirable feature of such a tool assembly is the capability to monitor one or more conditions at the site where the tool assembly has been located. In addition to such parameters as water level, temperature, and turbidity, it is also desirable to measure other parameters such water quality (i.e., the amount of contaminants in the water) which can be measured through the use of a conductivity sensor or other ion selective electrodes (ISE) sensors specially configured to detect the presence of one or more specific contaminants.
A significant issue with regards to the employment of tool assemblies for monitoring water quality conditions is the relatively high cost of each unit. One reason for the high cost is that they use expensive components and designs that frequently require a significant amount of expensive machining and assembly. The tools assemblies often require the complex assembly of many components and significant manufacturing expenses are often required to provide structures for coupling the components and for electrically interconnecting the components. Furthermore, assembly and disassembly of components of the down-hole tools frequently require the use of wrenches or other tools, and sometimes special tools. This complicates use of the down-hole monitoring tools, and providing features on the down-hole tools to accommodate tools required for assembly and disassembly often requires machining, which significantly adds to manufacturing costs. Furthermore, electrical interconnections between components typically require special keying of the components, or of the electrical connectors between the components which result in difficulty of use and a possibility for tool damage or malfunction due to misalignment.
In addition to the high cost of monitoring wells and down-hold monitoring tools, a significant amount of ongoing labor is typically required to maintain the tools and to obtain and use data collected by the tools. For example, it is frequently necessary to have someone visit the monitoring wells at periodic intervals to make sure that the tools are still working and to obtain data collected by the tools. Data must then be analyzed for use. The frequency between visits to a well may be a function of a number of variables, such as the reliability of the tools, the frequency with which batteries need to be replaced, and the capacity of the tools to collect and either store or provide access to the data. Moreover, many down-hole tools are difficult to service and must be returned to manufacturers and distributors for even relatively simple service tasks such as changing batteries in the tool. There is a significant need for tools that are simple to manufacture and assemble, require less attention, and are easier to service.